The coagulation of blood is such a prominent phenomenon that it has attracted attention at all times, and as a result numerous theories to account for it have been advanced. In recent years much experimental work has been done on the subject, the results of which have changed many of the former conceptions. In the blood of young organisms there is a tissue that is comparatively new in its body function and as yet has not been acted on by many external conditions. For this reason the substances involved in the coagulation of the blood of the new-born infant were studied.

The first study was based on a series of thirty-five new-born infants. The mothers had been under the care of the obstetric department and were on a standard diet1 during the prenatal period. The infants were fed regularly at four hour intervals, being sent to breast at the